Such an elongated luminaire is disclosed in EP-A-1758068, which publication describes a luminaire provided with an elongated lens extending parallel to the array of LEDs, whereby the array of LEDs and the lens have a common longitudinal plane of symmetry. The array of LEDs is arranged along a longitudinal axis. The luminaire comprises an elongated U-shaped body, the bottom of the body being provided with the straight array of LEDs. The elongated lens is clamped between the legs of the U-shaped body, in order to obtain the desired beam of light emitted by the luminaire.
Luminaires comprising a plurality of LEDs can be used as an alternative to conventional light sources, thus being capable of replacing typical fluorescent and incandescent luminaires. LEDs can emit bright light radiation, and a luminaire comprising a number of LEDs can be designed in such way that its light radiation is similar to or improved with respect to the light radiation of a conventional fluorescent or incandescent luminaire. The term “improved” here relates to a better horizontal uniformity.
In particular, the invention is related to an elongated luminaire for illuminating merchandise in a freezer cupboard having a number of neighboring transparent doors at its front side. Each door can hinge about a vertical axis, or can be shifted in its plane in the horizontal direction, so that the merchandise is approachable for a person who opens the door. The elongated luminaires are mounted behind the door cheeks or mullions, i.e. the vertical posts or jambs along both vertical edges of the doors when the doors are closed. The doors are hingingly connected with the door cheeks, and, in case of shifting doors, the doors can shift in front of the door cheeks. The luminaires illuminate merchandise behind the doors, such that the light beams of the luminaires behind two neighboring door cheeks overlap each other in order to illuminate the merchandise from two sides.
According to the prior art, the merchandise is illuminated by means of tube-like fluorescent luminaires mounted behind the door cheeks. When an array of LEDs is used for illuminating the merchandise, in particular LEDs having bright light radiation, the distance between the LEDs in the array will be substantial, for example 15 cm or more. Such a relatively large distance may result in a less uniform illumination of the objects in front of the luminaire.